And, AFAIK, there's very little market even for games that don't require a high end GPU on Mac. My guess is the majority people who want to play games on a desktop/laptop just know to get a Windows PC.
If you were a casual gamer, you'd be pretty satisfied on a Mac for that decade.
Things got significantly worse since the 32 bit support was dropped. Most companies aren't interested in going back to update a decades old game to support Mac gamers, so a ton of games that were available suddenly became unavailable. And with the M1, Bootcamp no longer works.
We'll have to see what the future brings. I never would have guessed things would have been as good as they were from 2009-2019, or that things would suddenly reverse as quickly as they did after 2019. So who knows what's around the next corner for Mac gaming.
There are lots of simple games in the App store, some ported from iOS, some indie games built on generic engines (Unity etc). The problem was Mac titles have to be continuously supported. Apple killed compatibility with older 32-bit games with Catalina which decimated my Steam library. I presume that's one of the reasons developers are not exactly flocking to mac en masse...
For example, games like Factorio are incredibly niche and loved by people with builder/engineer mindsets (not necessarily working as engineers). Now you've got to ask yourself whether potential Factorio players are more or less likely to own a Mac, compared to the 3% (cited by another commenter) of all Steam users on Macs.
Also I wonder how this 3% figure was calculated. Is it based on monthly active users? I am a Mac user and I have Steam installed but I don't leave it running all the time because application itself is a dumpster-fire battery hog. I only start it up when I want to play a specific game, then I shut it down. Some games don't even require Steam to be running so I launch them directly without bothering to start Steam. Am I excluded from the monthly active users because I might go months without launching Steam, despite playing games regularly?
That’s not nothing, and arguably if you have a good game, you’ll be one of the shining few on the Max.
Develop your game for x86_32, suddenly Apple drops support and you have to rewrite your entire game again for x86_64.
Develop your game for OpenCL/GL, suddenly Apple drops support and you have to rewrite your entire game again for Metal.
Develop your game for x86_64, suddenly apple drops support and you have to rewrite your entire game again for ARM64.
That's without counting the fact that most games developed nowadays developed using Vulcan or DX12 which has to be rewritten to Metal.
People are installing Windows on their Macs to play games that used to run natively on MacOS. Imagine how bad the backlash if this happened on Windows.